Mine roof support



June 16, 1953 R. N. KNIGHTS ETAL MINE ROOF SUPPORT s Sheets-Sheet 1Filed Aug. 31, 1949 June .16, 1953 R. N. KNIGHTS ETAL MINE ROOF SUPPORT5 Sheets-Sheet 2 Filed Aug. 31, 1949 Invent/ops @Cl/HIGD M nf/GCOL/1Y1)! Fk/a'i,

By@ m d g Attorneys June 16, 1953 KN|GHTs ETAL 2,641,906

MINE ROOF suPPbR'r Filed Aug. 31, 1949 5 Sheets-Sheet 3 Patented June16, 1953 MINE ROOF SUPPORT -Richard N. Knights, Hucclecote, and Colin M.Frye, Longlevens, England, assignors to Dowty Equipment Limited,Cheltenham, England Application August 31, 1949, Serial No. 113,454 InGreat Britain September 1, 1948 3 The present invention'consists in amine roof support comprising two sets of at least two rigidlyinterconnected props arranged one behind the other in parallel spacedrelationship, and means in the nature of parallel links connecting thetwo sets together side by side into a parallelogram, whereby when theprops of either set are loosened whilst thoseof the other remain held,the set of loosened props can be advanced by being moved relatively tothe other set under the influence of a force acting diagonally of theparallelogram. By thus linking the two sets together advancement cantake place by the one held set swinging with the parallel links aboutthe other loosened set, and so on alternately in a walking movement.

The support will generally be used with one end of each set being nearerthe coal face. When the cutting operation has proceeded sufliciently torequire support for the roof exposed between the coal face and thenearest supported section, the props of one set will be loosened andmoved forwardly nearer to the coal face. When the loosened set has beenadvanced, the props of this set will be extended to givethe additionalsupport required. In time, the other set of props will be loosened andsimilarly advanced to a new position of support.

Although the invention is applicable for use with many kinds of prop itis preferred to use hydraulically actuated props which may embody theusual relief valves for permitting the props to shorten under increasingroof pressure. If the props are of the hydraulic type, the pressurespaces of all the props of a set may intercommunicate so that thepressure can be developed from a single pump.

A further feature of the invention consists in providing between the twosets of props power driven mechanism for advancing the support set byset. A double-acting fluid-pressure operated jack may conveniently beused as an extensible and contractible link extending diagonally betweenlinked sets of props. When the jack is extended, the set at one side ofthe support will be advanced, and when the jack is contracted the otherset will advance, provided. of course that the stationary set is clampedbetween the roof and floor.

The invention further consists in a mine roof support comprising atleast two hydraulically actuated roof supporting units, meansinterconnecting, the units so that when one is held and the other isloosened, the loosened unit can be advanced by being moved relatively tothe held a 12 Claims; (01. 6185) one, and valvemechanism preventingeither unit from being loosened unless the other is taking apredetermined roof loading. Thus the hydraulic system associated withthe support may include primary valve mechanism permitting supply flowto the props of one set or unit whilst permitting return flow from theother, and vice versa, and secondary valve mechanism moveable inresponse to a predetermined pressure in the supply flow to move from aposition preventing such return flow to a position permitting such flow.The primary valve mechanism may serve also to permit pressure fluid toreach an appropriate end of an advancement jack while supplying theprops of one set and permitting return flow from the other end of thejack, and vice versa, means being provided for reversing the action ofthe primary valve mechanism upon the attainment of a predetere minedpressure in the system being supplied.

If the props are of the hydraulic type, and if the hydraulic systemsupplying them is controlled by valve mechanism in accordance with theinvention, the supply of pressure fluid along a single line will serveto bring about automatically a sequence of operations which causes themine roof support to be advanced step by step.

If the coal-getting installation includes a conveyer extending along thecoal face. the conveyer may, as the working face recedes, be advanced asa whole by means of a number of hydraulic roof supporting units having asingle valve mechanism in accordance with the invention, said supportsthus being controlled from a single control point.

A mine roof supporting installation incorporating the several featuresof the present invention will now be described in conjunction with theaccompanying drawings, of which Figures 1 and 2 illustrate the roofsupporting structure, Figure 1 being a side elevation partly in sectionand Figure 2 being a plan view partly in section; and Figure 3 is adiagrammatic representation of the hydraulic system associated with thestructure of Figures 1 and 2.

The roof supporting structure shown in Figures 1 and 2 incorporates atleast four upright hydraulic props, arranged in two sets, one set at theleft and the other set at the right. One prop in each set, II and I2,respectively, may be considered the forward prop and the other prop ineach set, Ila and I2a, respectively, will be the rear prop of its set.The props ll, Ha ,of one set are pin jointed to a roof bar It and to afloor bar 20, and the props [2, 12a of the other set are similarly pinjointed to the roof bar I9 and the floor bar 2|. These pin joints allowsome slight tilting of the individual roof bars and floor bars toaccommodate irregularities in the mine roof and floor. In addition, theprops I and i id of the right hand set are supported in and con nectedby a rigid side frame consisting of cross tubes l3 joining sleeves l4and Ma that surround and mount the respective props H and Ha. In similarmanner the props l2 and i202 of the left hand set are connected andmounted in the respective sleeves of a second such side frame made up ofsleeves i5 and iGa joined rigidly by cross tubes l5. The right hand sideframe and the left hand side frame are linked together by parallellinkage such as the four transverse links Ii, two connecting the top andbottom of the sleeves l4 and I6, and the other two connecting the topand bottom of the sleeves I ia and Mia. The links and the two rigid sideframes relative to which the ends of the links may swing constitute thusan articulated upright structure which can be deformed by effectingalternately approach of its diagonally opposite sleeves 14a and I5, andtheir separation, always maintaining their side frames in parallelism.Each prop, it will be observed from Figure 1, is permitted limited axialfreedom with respect to the sleeve of the rigid side frame wherein it ismounted, and this is required in order to accommodate irregularities inthe level of the mine roof and floor, through the pin joints alreadymentioned which connect the props to the roof bars i3 and the floor bars25, while avoiding the imposition of any undesirable stresses on therigid side frames and the links H which connect them.

The four props are structurally substantially identical with oneanother, and referring to the prop l2 in Figure 1 it will be seen thatthere is a lower outer tubular member 22 within which there is slidabletelescopically an upper inner tubular member 23. The tube 22 is closedat its lower end by a closure piece 24 and the tube 23 is closed at itsupper end by a head piece 25. At its lower end, the tube 23 is glandedat 25 to the tube 22. troduction of pressure fluid into the space withinthe tubes will cause the prop to extend, and that contraction ispermitted when the pressure fluid is allowed to leave the space.

Deformation of the upright articulated structure, such as has alreadybeen mentioned, can be accomplished by a double-acting hydraulicadvancement jack 23, 29 which is pin jointed at its respective ends tolugs 2'! fitted upon diagonally opposite sleeves such as and Ida. If,say, the props ll, Ha mounted in the right hand side frame M, Ma, iiiare extended between the roof and the floor to hold that side framefixedly in position, and the props l2, |2a mounted in the left hand sideframe t6, Ifia l5 are slacked or loosened, extension of the advancementjack 28, 29 will thrust forwardly the sleeve I6 and of course the entireleft hand side frame, by reaction from the fixed sleeve 14a and righthand side frame. The floor bar 2| will shufile forwardly over the floor,and the roof bar 19 also moves forwardly; the links H all swing aboutthe sleeves at their ends. If now the props 22, in are extended to fixthe left hand side frame It, Isa, i5 in the attained advanced position,and the props l I, Ila are loosened, contraction of the advancement jack2%, 29 will draw the sleeve Ma and the entire right side frameforwardly, reacting from the now fixed sleeve it, and so the entiremechanism can be walked forwardly by successive It will therefore beseen that the inopposite deformations of the upright articulatedstructure.

The support may with advantage be fitted with a valve box indicatedgenerally at 33 by which the sequence of operations necessary to effecta number of advancing movements or steps may occur automatically uponthe continued supply of pressure fluid along a single feed pipe 3 Thisvalve mechanism will now be described in detail with reference to Figure3 of the drawings.

The spaces within the tubes 22, 23 of the props IE and lidintercommunicate through a line 32 to which leads a common supply andreturn line 33, and the spaces of the other two props l2 and 52aintercommunicate through a pipe 34 to which ,leads a common supply andreturn line 35.

There are also two lines 36 and 3'! leading to opposite ends of the jackcylinder 23.

Liquid from a reservoir 38 is fed by a pump 39 to a manually operablecontrol valve 48 from which the liquid flows either through a returnline 4! back to the reservoir or through a single supply line 3| leadingto the valve 100x3 3. The supply line -3| opens into a chamber 42 fromwhich the liquid reaches the primary valve 43 of the system. The primaryvalve 43 is a piston valve which opens either one of the passages M and45 to the source of supply while placing the other of the passages "34and 45 in communication with a return line at leading back to thereservoir 38, In the position shown, liquid from the chamber 42 canreach the passage 15 through the port 47 and passage it, and the passage44 communicates with the return line 43 by way of the annular space 53around the valve 43. The passage 44 communicates directly with the pipeline 36 leading to one end of the jack cylinder 28, and leads through aspring loaded non-return valve 50 to the pipe line of the props I2 andI211. The passage similarly leads directly to the pipe 37 'connectedwith the opposite end of the jack, and through a spring loadednon-return valve 5| to the pipe line 33 of the props and I la. Thenonreturn valves 59 and 5| are adapted to be unseated by projections 52and 53 respectively formed on the opposite ends of a piston 54 and thusconstitute a coordinated control valve means operatively interposedbetween the primary control valve and the props of the respectiveframes. The piston 54 is shown in a mid-position at which neitherprojection engages its valve, and it may be assumed that the roofsupport has been standing for a time and that the piston 54 has assumedthis mid-position due to leakage in the valve 33. All the props arereacting against the roof, and if necessary could support a maximum roofloading of say tons for each pair of props which is the limit imposed byrelief valves 55 and 5B controlling flow from the pipe lines 33 and 35to the return line 46. By arranging the two relief valves 55 and 55 witha common spring 5? between them, the relief valve of either system, whenoperating alone, will limit the roof loading for the set of props to 50tons, whereas if the two relief valves should operate simultaneously, asmay happen after the support has been standing in use for a period oftime, each set of props will be capable of supporting 50 tons loading sothat the support as a Whole will withstand a loading of tons.

In the example being describedit is desired that when a set of props isloosened, each prop of the set shall be supporting a roof loading of 1ton which is overcome by the jack when the latter is effecting anadvancing movement. For

this purpose the pipe lines 33 and 35 each include in parallel anon-return valve 58' preventing flow away from the props and a reliefvalve 59 permitting return flowonly when pressure in the line'is above apressure atwhich each prop supports the roof loading of 1 ton.

'When the primary valve l3 is in its up-posit'ion shown, pressure'fluid.will reach the props Hand I la through the'non-return valve 5|, and willreach the lower end of the jack 28 through the line 31. The piston 54 ofthe valve box and its projections 52 and 53 act as a differential-areapiston, as will later be explained, limiting the setting pressure of theprops- I l andl In. to a roof loadingof 5 tons, the projections 52 and53 each being 6 of the cross-sectional area of the piston 54.

During operation of'the system it is necessary for the primary valve 43to reverse its action and change-over from one extreme position to theother-as soon as possible after one set of props has reached the settingpressure of 5 tons, and the other set hasbeen relieved down to one ton,and before going on to explain the operation of the system it'isnecessary to describe the mechanism by which this reversal is achieved.

Thevalve43 has a stem 50 extending into the chamber 42, said stem havinga longitudinal slot 6| through which extends a pin '62 at one end of alink 63 which latter thereby has lost motion connection with the stem50. The other end of the link 63 is pivoted at 64 to a rocking plate 65which rocks about a pivot 66 on a'bracket 61. The plate 65 can swingdown against the resistance-of apair of snap-over springs one of whichis shown at 68 extending between abutments on the rocking plate and on afurther fixed bracket 69. As the rocking plate is caused to'move down,as will be explained, the abutment of the springs with the plate '55passes through a dead centre position after which the action of theexpanding springs68 causes the plate 65 to move down with rapid positivemovement during which the pin 62 in the slot 6| in the valve stem 60engages the inner end of the slot and shifts the valve 43' to its otherextreme position.-

The rocking plate 65 has a slot 10 through which extends a pin H on alink 12 connected at the upper end of a plunger I3 which extends througha gland 14 into a chamber 15 where the plunger carries a head it whichis spring biassed by a spring 11 so that the plunger i3 tends to projecta maximum amount into the chamber 42.

The slot '10 in the plate 65 isdisposed in relation to the axis of theplunger 13 so that it forms in effect one side of a V with the pin H atthe upper end of the slot. The fluid pressure in the chamber 42 actsupon the end of the plunger 13 and when the pressure has reached apredetermined pressure, the plunger will be moved against its springs 11to cause the pin H to rock the plate 65 in a clockwise direction thuscausing the spring 68 to compress through the dead centre positionalready mentioned. It will be appreciated that the pressure in thechamber 42 at which the trip mechanism changes over the po sition of theprimary valve 43 in this way, will correspond to a pressure somewhatabove that at which the props obtain their setting pressure of 5 tonsroof support. As soon as the springs 68 expand after one end thereofpasses through the dead centre position, the rapid movement of therocking plate as, given by the snap-over springs 68, causes the pinconnection with the link 12 to take up a position at the other 6 end ofthe slot 10, which slot-has moved so that it new forms the other side ofthe V. The'pin H now engages a notch at said other end, and-the rockingplate '55 is held in its new angular position by the expansion of thespring 68 after the latter had passed through the dead centre position.The springs 63 now extend down to the left. The plunger 13 is again Iprojecting the maximum amount into the chamber 42 ready to be depressedwhen the pressure of the fluid in the chamber 42 again reaches thepredetermined value. When the'plunger 13 is again depressed. the link'12will rock the plate in an anti- I clockwise direction to carry thesnap-over spring advancement of the mine roof support will now bedescribed, it being assumed that all the parts are in the Positionsshown in Figure 3. In these positions all the props are reacting betweenthe roof andfloor and when the pressure. fluid is supplied into thepassage 45 and pipe lines 33 and 31' the jack will meet resistance andthe pressure will build up below the piston 54 of the secondary valvemechanism. The piston 54 will therefore rise and open "the valve 50 torelieve the props l2 and lZa by placing the pipe line 35 incommunication with the return line it. The supply of pressure fluid tothe jack will not result in any movement of the support because the jackis fully contracted. Pressure will therefore build up in the chamber 42housing the trip mechanism and when this pressure reaches the propervalve the valve 43 will be moved automatically into its lower positionat which the passage 44 is in communication with the chamber 42, and thepassage 45 is in communication with the return line 46 by way of theannular space 49 around the valve 43. The changeover of the valve willalso place the line 31 from the lower end of the jack in communicationwith the return line 45, and place the line 36 at the upper end of thejack in communication with the pressure fluid supply in the chamber 42.Thus directly the valve 43 has moved to its lower position pressurefluid will be applied to the upper end of the jack which will move therelieved props l2 and lZa into the dotted line position. At the sametime pressure fluid will be supplied along the line 35 leading to thenewly advanced props I2 and 12a and once the jack has reached the limitof its travel pressure will build up in the props l2 and I2a until thesetting pressure of 5 tons roof support is reached, and just above thispressure the piston 54 will be moved down to allow the valve 50 to closeand to open the valve 5| to relieve the props i l and i la whereafterpressure will build up in the chamber 42 and. so that the trip mechanismwill return the valve 43 to its upper position. This sequence ofoperations will continue as long as pressure fluid is supplied to thevalve box along the single supply line 3 I. I

The pressure seouence may be summarised as follows: The jack movesrelieved props when the relieved props are taking a l ton-roof loadingand while the other props are taking at least 5 tons. The props moved bythe jack are then raised to a '5 ton loading and the other props arerelieved by the corresponding non-return valve 50 or 5| opening. Thetrip chamber pressure then reverses the slide valve at a pressure alittle above the setting pressure of 5 tons. The hydraulically lockedprops are relieved by way of relief valve 55, 56 at 50 tons pressure perside of thestructure.

The valve mechanism above described for a single roof supporting unitmay serve to control the advancing movements of a number of such units,and these units may be placed at intervals along the length of aconveyor in order to shift the conveyer as a whole as a consequence ofshifting the several roof supporting units. Although in the exampledescribed the props of one set are said to be loosened while stillsupporting a roof loading of 1 ton, they may be entirely freed from theroof before the jack causes them to advance. In any event the secondaryvalve mechanism comprising the piston 54 and the non-return valves 56and 51 prevent either set of props from being loosened until the otherset is taking a predetermined roof loading.

If desired manually operable means may be provided whereby the props ofa support may be relieved at will. For example the pipe lines 53 and 35,between their respective props and nonreturn and relief valves 58 and59, may be fitted with cocks operable separately 01' together to placesaid lines in connection with the reservoir.

We claim:

1. A mine roof support comprising at least four constrictable andexpansible upright hydraulic props disposed in two sets at right andleft, respectively, and one prop ahead and one prop behind in each set,said props being of a length, when extended, to rest upon the floor andto support the roof, a rigid frame connecting and supporting the forwardand the rear props, respectively, in the set at the right, and a likerigid frame connecting and supporting the forward and the rear props inthe set at the left, parallel linkage means connecting the forward endsand the rear ends of the two frames, to constitute with the frames adeformable parallelogram, extensible and contractable power meansextending diagonally of such parallelogram between and connected to theforward end of one frame and the rear end of the other frame, andoperable upon contraction to shorten the distance between its two pointsof connection, and upon extension to length such distance, hydrauliccontrol means shiftable between two limit portions, and operable when inone such position to extend the two props at one side to hold fast theseprops and their frame between the floor and the roof, and operable whenin its other limit position to constrict the other two props at theother side to loosen them and their frame, and vice versa, and furthercontrol means to alternately extend and retract said power means,whereby the loosened props and their frame may be advanced relative tothe held-fast props by appropriate contraction or extension of suchdiagonally extending power means in coordination with extension andconstriction of the respective sets of props.

2. A mine roof support comprising four constrictable and expansibleupright hydraulic props disposed in two sets at right and left,respectively, and one ahead and one behind in each set, said props beingof a length, when extended, to rest upon the floor and to support theroof, a rigid frame including two spaced parallel upright sleevesconnecting and supporting the two props at the right, and a like rigidframe including two spaced parallel upright sleeves connecting andsupporting the two props at the left, each prop being mounted by itssleeve with a limited freedom of independent axial movement therein, a

link connecting the forward ends of the two frames, and a similar linkconnecting the rear ends of the two frames, to constitute with theframes an articulated structure wherein one frame can swing about theother in parallelism, a double-acting hydraulic advancement jackextending diagonally between and pivotally connected to the forward endof one frame and the rear end of the other frame, control meansoperatively connected to said advancement jack to contract the same andso to shorten the distance between its two points of pivotal connection,and alternately to extend the same to lengthen such distance, andfurther control means operatively connected to the several props andcontrollable to extend the two props at one side to hold fast theseprops and their frame between the floor and the roof as a point ofreaction, and at the same time to constrict the other two props at theother side to loosen them and their frame for advancement by reactiontherefrom, and vice versa, whereby the loosened props and their framemay be advanced relative to the held-fast props by appropriatecontraction or extension of the diagonally extending advancement jack.

3. A mine roof support as in claim 1, wherein the parallel linkage meansinterconnecting the two frames comprise an upper and a lower transverselinks connecting the forward portion of each frame and two like linksconnecting the rearward portions of each frame in the parallelogramarrangement, to maintain each frame upright by support from the otherframe when the props of either frame are loosened whilst those of theother frame are held fast, and the loosened props and their frame isadvanced by being swung uprightly about its connections to the held-fastset.

4. A mine roof support as in claim 1, including a single pressure fluidsource operatively connected to the props of both frames, and thefirstmentioned hydraulic control means is operatively connected betweensaid source and alternatively the props of one frame or the props of theother.

5. A mine roof support as in claim 2, including a single pressuresource, conduit means connecting said source, by way of the controlmeans for the advancement jack and thence to the further control meansfor the props, and for relief from the same, and a selector deviceincorporated in said further control means to regulate access ofpressure fluid to one or the other set of props, and relief from theother set, in accordance with the setting of the first control means forextension or for retraction of the advancement jack.

6. A mine roof support as in claim 2, including a primary control valvegoverning thedirection of supply of pressure fluid to one or the otherend of the advancement jack, and a coordinated secondary control valvemeans operatively interposed between the primary control valve and theprops of the respective frames, and automatically shiftable by pressurefluid, according to whichever end of the double-acting jack is suppliedwith pressure fluid, to deliver the pressure fluid likewise to theforward props for their holding fast, and to relieve the rearward propsfor their loosening.

7. The combination of claim 2, and means automatically operable bycompletion of an advance cycle to shift the control means for theadvancement jack, and thereby to condition the mechanism for reversemovement of said jack at commencement of the neXt cycle.

8. A mine roof support as in claim 6, including means sensitive to backpressure from a held-fast set of props, automatically operable toreverse the primary valve, to reverse thereby the direction of actuationof the double-acting jack, for advance of the loosened set of props.

9. A mine roof support as in claim 1, including a single pressure fluidsource operatively connected to the props of both frames, means oprableto connect said source alternatively to the props of one frame or theother, and valve means automatically operable toblock connection of thefluid supply source to loosen the props of one frame unless those of theother frame are loaded to a predetermined value.

10. A mine roof support asin claim 2, including a single fluid pressuresource operatively con- I nected to the props of both frames and to theopposite ends of said advancement jack, a reversible primary valveconstituting the first-mentionedcontrol means, and governing delivery ofpressure fluid to the respective ends of said 1 jack, and tosecondaryvalve means constitutingv the further control means, said secondaryvalvemeans including two spaced-apart non-return' valves in separate conduitsto the props of the respective frames, and a double-acting differentialarea piston interposed between said non-return valves, movable under theinfluence of predetermined pressure in the conduit not being supplied.

11. A mine'roof support as in claim 1, including a single pressure fluidsource operatively connected to the props of both frames, thefirst-mentioned control means being operable to connect said sourcealternatively to the props of one frame or the other, and a branchrelief line off the pressure line to each set of props, and a reliefvalve in each such pressure line openable .at a predetermined maximumroof loading. I

12. A mine roof-support as in claim 11, including a single loadingspring common to the two individual relief valves, urging either or bothto closed position.

